Is there English proverb equivalent to Japanese and Korean one, “The ground becomes solid after a heavy rain”?

In the speech after toasting at the dinner party hosted by President of the Republic of Korea subsequent to the Meeting of Three-country (China, Japan and Korea - in Alphabetic order) Leaders held in Seoul on November 1st, President Park of the Republic of Korea addressed that three countries can establish closer relationship by promoting mutual trust and cooperation as a common Oriental proverb, “the ground becomes more solid after going through a heavy rainfall” goes.

“雨降って地固まる ‐ the ground becomes solid after a heavy rain” is a very popular saying in Japan, and possibly both in China and Korea, to describe the familiar fact that things turn out better and relationship becomes much closer after going through a span of discords and quarrels like a married couple.

Are there counterpart proverbs in English to “the ground becomes solid after a heavy rain”?

Maybe "April showers bring May flowers," meaning that "a period of discomfort can provide the basis for a period of happiness and joy."

Consider,

What doesn't kill you makes you stronger or That which doesn't kill you makes you stronger

: used to express the sentiment that hardship or difficult experiences build moral character. Wiktionary

雨降って地固まる (ame futte ji katamaru) “The rain falls, the ground hardens” is what this phrase is telling us. Basically, numerous storms and downpours will cause the soil to toughen up. We should, however, remember that rain is often associated with feelings of sadness and pain. So if that pain causes our own selves to toughen up, we can say that “What doesn’t kill you makes you stronger”. Green Tea Graffiti

I would suggest using "every cloud has a silver lining":

Every difficult or sad situation has a comforting or more hopeful aspect, even though this may not be immediately apparent:

The 3-way relationships among the countries have strained over the past years because of some territorial and historical issues. I think Park mentioned the proverb to mean that "there is still a silver lining (hope/solid ground) even though they are going through clouds (heavy rain: difficulty and uncertainty in reaching any agreement on those issues)."

[Oxford Online Dictionary]

One that I hear from time to time:

It's always darkest before the dawn.

Meaning, "even when things seem terrible, a change for the good may be just around the corner." The nuance is quite different of course, and it has a bit of melodrama baked in, which may not match the apparent subtlety of the original.